In the retail industry, self-service checkout terminals and assisted checkout terminals are used to tabulate the prices for the items chosen by a customer for purchase and to present the customer with a grand total price at the end of the transaction. Many of such checkout terminals comprise a product scale that is used to weigh an item that is sold by weight (e.g., for a fixed price per pound.) When the customer (or a clerk) places an item on the product scale, the customer or clerk must often enter a product lookup code (PLU) into the checkout terminal or otherwise identify the weighed item to the checkout terminal. It is known that unscrupulous persons sometimes seek to fraudulently enter an incorrect PLU into the checkout terminal in order to minimize the cost registered by the checkout terminal for a given item. For example, a customer at a self-service checkout terminal may place a beef steak on the product scale but enter the PLU code for bananas. If the beef steak were selling for $8.99 per pound but the bananas were selling for $0.99 per pound, then the customer would fraudulently save $8 per pound on the beef steak. In another example, the customer could place an expensive (yet lightweight) item on the product scale such as a digital versatile disc (DVD) containing a copyrighted movie and enter in a PLU code for a produce item (such as bananas) selling for a very low price per pound.
Such problems are especially acute for self-service checkout terminals where the customer can enter the PLU code into the checkout terminal himself. Yet the problem can also occur at traditional assisted checkout terminals if the clerk at the terminal acts in collusion with the customer. It is well known that unscrupulous clerks sometimes assist their friends or acquaintances to obtain items at low cost by improperly identifying the items using a PLU code or other means.